1. Charlotte-Rock Hill-Gastonia MSA Summertime Ozone Formation
Photos from 2001 Mecklenburg Country State of the Environment Report

2. Arizona’s Valley of the Sun “Brown Cloud”
Phoenix photo from accessed Mar 2004
Observed since early 1990’s; contains C Particles and NO2 (brown) gas
From burning fossil fuels: cars, construction equipment, power plants, lawn mowers, leaf blowers contribute to this brown cloud
Weather also a key factor

3. Image take from http://www. al. noaa. gov/WWWHD/Pubdocs/TropoRural
Image take from accessed Mar 2004

4. Presence of NO2 (brown gas) results in inevitable formation of ozone
NO2 (brown) + sunlite  NO• + O•
O• + O2  O3 (Ozone)
Control measures to effectively address ground-level ozone must focus on minimizing NO2 formation

5. Ozone precursors Nitrogen Oxides
Dry Air is 78% Nitrogen (N2), 21% Oxygen (O2)
Heating air to high temperatures forms NO• (motor vehicles, fossil-fuel power plants, lightning)
NO• is an ozone precursor and also reacts directly with ozone to destroy it
Volatile Organic Compounds (VOC’s)
VOC’s continuously emitted by fuel spills, motor vehicles, trees, air fresheners, paints, and countless other sources
OH• hydroxyl radical is the atmosphere’s “natural detergent” that cleans VOC’s from the air by initiating the process that converts them into carbon dioxide and water

6. Volatile Organic Compound (VOC) Removal
Air’s natural VOC cleanser produced from ozone and water
Ozone (O3) + UV-B -> O2+ *O•
*O• + H2O  2OH•
OH• works by transforming stable VOC molecules (R-H) into reactive radicals (R•)
OH• + R-H  R• + H2O
Reactive organic radicals immediately combine with oxygen to form peroxide radicals
R• + O2  (R-O-O•)

7. Formation of Nitrogen Dioxide
NO• + R-O-O•  NO2• + RO•
Formation of NO2 (and O3) driven primarily by:
Concentration of VOC’s (near emission sources)
Concentration of NO• (rural & downwind areas)
Concentrations of both NO• and VOC’s
***Summertime ozone pollution results from an overload in our air of NO•, VOC’s, or both

8. NO and VOC Effects on Ozone Production
Both NO• + VOC Sensitive
VOC
Sensitive
Region
NO•
Sensitive
Region
Both NO• + VOC Sensitive
Figure from : accessed Mar 2004

9. ’95-’99 AM NMOC/NOy Ratios for the Plaza Monitoring Site20 NO
Limited x 15 y
NMOC/NO 10
VOC Limited 5
1994
1995
1996
1997
1998
1999
2000
From Perry, JL and Owens, PM, “Weekday/Weekend Variability and Long-Term Trends in Traffic, CO, NOy, and Ozone for the Charlotte Metropolitan Area during the 1990's, AWMA, June 2001

10. I-77 Traffic Volume vs. Time of Day
5000
4000
3000
Hourly Volume
2000
1000
Time of Day (Hour)
Sun
Mon
Tues
Wed
Thu
Fri
Sat
From Perry and Owens, AWMA, 2001

11. May-Sep ‘95-‘98 Plaza Average Hourly NOy40 y 35 30 25
Avg Hourly NO
Concentration (ppb) 20 15 10 5 1 3 5 7 9 11 13 15 17 19 21 23
Time of Day
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
From Perry and Owens, AWMA, 2001

12. 1990-1998 May-Sep Diurnal Charlotte Ozone Averages
By Day of Week (weekend days-lines, weekdays-markers
From Perry and Owens, AWMA, 2001

13. Obtained from John White, NC DAQ

14. From: http://www. epa. gov/airnow/showmaps. html
From: accessed Mar 2004

15. From: http://www. epa. gov/airnow/showmaps. html
From: accessed Mar 2004